Systems and Methods for Determining Optimal Atrioventricular Pacing Delays Based on Cardiomechanical Delays

Abstract

Techniques are provided for use with implantable medical devices such as pacemakers for optimizing atrioventricular (AV) pacing delays for use with cardiac resynchronization therapy (CRT). In one example, the end of atrial mechanical contraction and the onset of isovolumic ventricular mechanical contraction are detected within a patient in which the device is implanted based on cardiomechanical signals, such as cardiogenic impedance (Z) signals, S1 heart sounds or left atrial pressure (LAP) signals. Then, a cardiomechanical time delay (MC_AV) between the end of atrial contraction and the onset of isovolumic ventricular contraction is determined. AV pacing delays are set based on MC_AV to align the end an atrial kick with the onset of isovolumic ventricular contraction. Thereafter, pacing is controlled based on the AV pacing delays.

1 . A method for use with an implantable cardiac rhythm management device for implant within a patient, the method comprising:
 detecting an atrial mechanical contraction within the patient based on cardiogenic impedance signals sensed by the device;   detecting an onset of isovolumic ventricular mechanical contractions within the patient based on the cardiogenic impedance signals;   determining a time delay from the end of atrial mechanical contraction to the onset of isovolumic ventricular mechanical contraction;   setting atrioventricular (AV) pacing delays based on the time delay; and   controlling pacing based on the AV pacing delays.   
     
     
         2 . The method of  claim 1  wherein detecting the atrial mechanical contraction includes detecting cardiogenic impedance signals along at least one atrial impedance vector oriented to detect atrial contractions and then identifying the atrial mechanical contraction within the impedance signals. 
     
     
         3 . The method of  claim 2  wherein the device is equipped with at least a right atrial (RA) lead and a multi-pole left ventricular (LV) lead and wherein the atrial impedance vectors include an electrical current injection vector between an RA tip electrode and an LV proximal ring electrode and an impedance-responsive voltage sensing vector between the RA tip electrode and an LV middle ring electrode. 
     
     
         4 . The method of  claim 2  wherein the device is equipped with at least a bipolar RA lead and a multi-pole LV lead and wherein the atrial impedance vectors include a bipolar electrical current injection vector between RA tip and ring electrodes and a bipolar impedance-responsive voltage sensing vector between adjacent LV ring electrodes. 
     
     
         5 . The method of  claim 2  wherein the device is equipped with at least an RA lead and a multi-pole LV lead and wherein the atrial impedance vectors include a unipolar electrical current injection vector between an RA electrode and a device housing electrode and a unipolar impedance-responsive voltage sensing vector between a proximal LV ring electrode and the device housing electrode. 
     
     
         6 . The method of  claim 1  wherein detecting the onset of ventricular mechanical contraction includes detecting cardiogenic impedance signals along at least one ventricular impedance vector oriented to detect ventricular contractions and then identifying the onset of ventricular mechanical contraction within the impedance signals. 
     
     
         7 . The method of  claim 6  wherein the device is equipped with at least LV and right ventricular (RV) leads and wherein the ventricular impedance vectors include a bipolar electrical current injection vector between RV tip and LV tip electrodes and a bipolar impedance-responsive voltage sensing vector between LV ring and RV ring electrodes. 
     
     
         8 . The method of  claim 6  wherein the device is equipped with at least LV and RV leads and wherein the ventricular impedance vectors include a bipolar electrical current injection vector between RV tip and ring electrodes and a bipolar impedance-responsive voltage sensing vector between LV tip and ring electrodes. 
     
     
         9 . The method of  claim 1  wherein the device is equipped to employ hybrid vectors that include a large field vector to injected current vector and a sensed local cardiogenic impedance (CI) vector. 
     
     
         10 . The method of  claim 9  wherein the large field vector includes one or more of an SVC-can vector, an RV ring to can vector and an RV ring to SVC coil vector. 
     
     
         11 . The method of  claim 9  wherein the sensed local CI vector includes one or more of an LV proximal ring to SVC vector and an LV proximal ring to can vector for detecting atrial impedance (Z) signals and multiple LV electrode to can vectors for detecting ventricular Z signals. 
     
     
         12 . The method of  claim 1  wherein detecting the atrial mechanical contraction is performed to detect an end of the atrial contraction. 
     
     
         13 . The method of  claim 12  wherein detecting the end of atrial mechanical contractions includes:
 detecting values representative of left atrial pressure (LAP) within the cardiomechanical signals sensed by the device; 
 detecting an increase in LAP prior to a QRS complex detected within an intracardiac electrogram (IEGM) sensed by the device; 
 detecting a first subsequent peak in LAP; and 
 identifying the end of atrial mechanical contraction as coinciding with the peak in LAP. 
 
     
     
         14 . The method of  claim 13  wherein setting AV pacing delays based on the time delay from the atrial mechanical contraction to the onset of ventricular mechanical contraction includes:
 calculating the time delay (MC_AV) as the delay from a first peak in LAP to a first valley in LAP. 
 
     
     
         15 . The method of  claim 1  wherein detecting the onset of ventricular mechanical contractions includes:
 detecting values representative of one or more of LAP, RVP, LVP, PPG signals and heart sounds within the cardiomechanical signals sensed by the device; and 
 detecting the onset of isovolumic ventricular mechanical contraction based on the detected values. 
 
     
     
         16 . The method of  claim 1  wherein detecting the ventricular mechanical contraction includes setting a ventricular event detection window. 
     
     
         17 . The method of  claim 1  wherein all of the steps are performed by the implantable medical device. 
     
     
         18 . The method of  claim 1  wherein at least some of the steps are performed by an external device based on signals received from the implantable medical device. 
     
     
         19 . A system for use with an implantable cardiac rhythm management device for implant within a patient, the system comprising:
 an atrial mechanical contraction detection system operative to detect atrial mechanical contractions within the heart of the patient based on cardiomechanical signals detected within the patient by the device;   a ventricular mechanical contraction detection system operative to detect the onset of isovolumic ventricular mechanical contractions within the heart of the patient based on the cardiomechanical signals;   a cardiomechanical time delay determination system operative to determine a time delay between the atrial mechanical contraction and the onset of ventricular mechanical contraction;   an atrioventricular (AV) pacing delay determination system operative to set AV pacing delays based on the time delay; and   a pacing controller operative to control pacing based on the AV pacing delays.   
     
     
         20 . A system for use with an implantable cardiac rhythm management device for implant within a patient, the system comprising:
 means for detecting atrial mechanical contraction within the heart of the patient;   means for detecting an onset of isovolumic ventricular mechanical contraction within the heart of the patient;   means for determining a time delay between the atrial mechanical contraction and the onset of ventricular mechanical contraction; and   means for setting atrioventricular (AV) pacing delays based on a time delay from the atrial mechanical contraction to the onset of ventricular mechanical contraction.